Researchers shed light on intron evolution

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By comparing four fungal genomes, researchers from MIT and the Broad Institute have described some of the dynamics of the evolution of introns, the non-coding portions of genes that comprise a large proportion of many genomes.

Introns are found in eukaryotic species, which includes all members of the fungi, plant, and animal kingdoms. Although introns were first discovered almost 30 years ago, scientists are still asking basic questions about their role.

The researchers studied fungal genomes that together span 400 million years of evolution from a common ancestor.

Their findings, published in the December 2004 issue of the Public Library of Science, describe how an increase in introns plays a significant role in eukaryotic evolution.

"Our results provide clues about two fundamental unanswered questions about genome evolution--how introns are gained and how introns are lost," said Chris Burge, Whitehead Career Development Associate Professor in MIT's Department of Biology.

Introns are one of the basic characteristics of eukaryotic genomes, said James Galagan, a computational biologist at the Broad. "We want to understand what they are doing because they comprise a significant part of our genomic ecosystem," he said.

To paint a more complete picture of intron evolution, the researchers are currently looking at other fungal genomes. With additional data and analysis, they hope to one day apply their whole-genome method to better understand intron evolution in the genomes of higher eukaryotes, including animals and plants.

Also on the study team are Bruce Birren, co-director of the Sequencing and Analysis Program and director of the Microbial Sequencing Center at the Broad; and co-first authors Cydney Nielsen, a graduate student in biology, and Brad Friedman, a graduate student in biology and mathematics.

This research was supported by grants from the National Institutes of Health, National Science Foundation, United States Department of Agriculture, and the Burroughs Wellcome Fund.